I'm trying to set the value in one table to the sum of the values in another table. Something along these lines:
SET field1 = SUM(table2.field2)
INNER JOIN table2 ON table1.field3 = table2.field3
GROUP BY table1.field3
Of course, as this stands, it won't work - SET doesn't support SUM and it doesn't support GROUP BY.
I should know this, but my mind's drawing a blank. What am I doing wrong?